For propping up the assembly for riveting, I took yet another suggestion from Mike Bullock's build log and made some vertical stands for the aileron that were tall enough the hold the nose skin off of the table. I used some round head screws to secure each end of the spar to the stand, then used clamps to secure the stands to the workbench.
The result was a remarkably solid assembly that wouldn't move a millimeter while I riveted everything.
Now I just had to figure out how the heck I was going to rivet the skin, especially toward the middle of the spar. Since I wasn't willing to buy any kind of specialized bucking bar for this task, I decided to modify the one I have to make it work better for this application. The only issues with the stock bucking bar are a) it's very difficult to keep a grip on the thin bar when your arm and hand are wedged into the tight interior space, and b) the bar is small enough to fall between the lightening holes and cause damage to the nose skin underneath while making it difficult to retrieve.
To solve both these issues I took a small wood block, sanded it smooth on all sides and edges to prevent scratches, then taped it to the bucking bar so it would sit flush on the bottom edge. This gave me a bucking bar that was easy to grip, easy to keep square, and wouldn't fall through the holes in the spar.
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| The masking tape wasn't my first choice, but it worked just fine. |
Now came the difficult part - actually riveting this thing. In order to get the bucking bar into the assembly I had to pry the bottom skin from the spar and slip it in place, though that's the easy part. The worst part of the whole process is having to maneuver my whole left arm into this space to hold the bucking bar in place for riveting. After some trial and error (and after putting a couple of old socks on my arm to keep the aluminum edges from digging into my skin) I managed to find a position that was comfortable and stable enough to work.
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| This is what I was dealing with. It's hard to see what you're doing, but I still managed to get decently consistent results. |
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| Not bad for working blindly! |
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| I never get tired of seeing lines of rivets slowly become finished. |
The modified bucking bar worked beautifully, except it wasn't able to stay flush for rivets directly under or adjacent to the stiffeners. I skipped those until the rest of the rivets could be set, then I removed the wood block from the bar. I could set the bar flat on the spar and it would fit neatly under each stiffener so I could set the remaining rivets.
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| As easy as this was, I asked myself why I didn't try this for the rest of the rivets. The main reason was the slight acute angle of the spar which causes these rivets to be slightly crooked when set this way, so my earlier method is still preferred. |
Once the line of rivets on the top of the spar was finished I squeezed the rivets attaching the leading edge skins to the nose ribs.
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| This was a ten-minute job, a cake walk compared to the rivets on the spars. |
Next was blind riveting the counterbalance pipe to the skin. I flipped the aileron over and made sure it was laying flat, then broke out the CS4-4 rivets and my blind rivet puller. I'm glad I dimpled the skins here because all of the rivets ended up laying almost perfectly flush. Finally, I could close out the bottom skins by blind riveting them to the spars. Once again I made sure each aileron laid flat before starting and I kept checking this as I worked.
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| Using a hand rivet puller for both ailerons (around 84 CS4-4 rivets pulled) was murder on my wrists. A pneumatic rivet puller would have been much appreciated here. |
At last I had both ailerons finished!
Since I definitely didn't want to try hanging these on the wall with their heavy counterbalances, I cleared off the top part of some shelves and stored them up there. To prevent moisture collecting from skin-to-shelf or skin-to-skin contact I made some cardboard spacers to create a small gap between each surface. If I have to continue storing these in the garage then I'll need to be vigilant for corrosion.
